1. Effect of 2000-2050 global change on ozone air quality in the United States Shiliang Wu, Loretta Mickley, Daniel Jacob, Eric Leibensperger, David Rind (GISS), David Streets (ANL) Harvard University Oct. 12, 2007 work supported by the EPA-STAR program

2. Models and future scenario Chemistry, transport, deposition, etc GHG Air pollutants & their precursors Climate Change GISS GCM 3 23 vertical layers extending to 85 km Horizontal resolution of 4º x 5º GEOS-Chem detailed ozone-NOx-VOC-aerosol chemistry Anthropogenic emissions (IPCC A1B scenario) Natural emissions Radiative forcing GCAP (Global Change and Air Pollution) model

3. Trends of NO x emissions from fuel use (2050 / 2000) ( IPCC A1B scenario ) Global changes in anthropogenic emissions - 40% +90% +800% +300% 4 2 1.5 1.1 0.9 0.8 0.7 0.6 0.5 Global total NO x emissions: + 90%

4. A1B 2000-2050 changes in climate Annual mean surface temperature +1.6 K Temperature: 2050 – 2000 Humidity: 2050 / 2000 20002050  NO x -lightning, Tg N/yr 4.95.8+18% NO x - soil, Tg N/yr6.16.6+8% Isoprene, Tg C/yr430537+25%

5. +1.6% +17%+18% 2050 climate / 2000 2050 emission / 2000 2000 2050 / 2000 Effects of 2000-2050 global change on tropospheric ozone (annual zonal mean)

6. Effects of 2000-2050 global change on tropospheric ozone (annual surface afternoon mean) 2050 climate – 2000 2050 emission – 2000 2000 2050 – 2000

7. Policy relevant background (PRB) ozone (summer afternoon)

8. Effects of 2000-2050 global change on U.S. ozone air quality 2000 2050 climate – 2000 2050 emission – 2000 2050 – 2000 Daily max 8h-avg ozone averaged over JJA (ppb) Increase of summer max- 8h-avg ozone by 1-5 ppb in large areas of U.S. due to 2000- 2050 climate change. Less effects in western U.S. because (1) increase of ozone from intercontinental transport and (2) anthro. emissions are low there.

9. Changes in summertime air pollution meteorology due to climate change Surface temperature (2050 – 2000) Convective mass flux (2050 - 2000) Mixing depth (2050 / 2000) Soil moisture (2050 / 2000) 1.0 0.8 0.6 0.5 -0.5 -1.5 -2.0 [g/m 2 /s] oCoC

10. What’s more: decrease of cyclone frequency Eric M. Leibensperger, Harvard 1999-20012049-2051 Summertime cyclones decrease by 17% in the 2050 climate

11. Cumulative probability (%) Midwest Southeast Northeast Cumulative probability distributions of max 8-hr ozone (JJA) climate change has more effect on the pollution events than on the means Max. 8-hr-avg ozone Cumulative probability (%) Max. 8-hr-avg ozone 2000 conditions 2050 climate 2050 emissions 2050 climate & emis Northeast Southeast Midwest Max. 8-hr-avg ozone Cumulative probability (%) median 99 th percentile

12. Cumulative probability (%) Why climate change has the most effects on pollution events? Max. 8-hr-avg ozone 2000s conditions 2050s climate 2050s emissions 2050s climate & emis median 99 th percentile Midwest Daily maximum temperature (K) Cumulative probability (%)

13. Mitigation of climate change penalty by reductions in anthropogenic emissions “climate change penalty” for ozone AQ = Δ[O 3 ] from climate change Reductions of anthropogenic emissions significantly mitigate the “climate penalty” and can even turn it into a “climate benefit” in the Southeast and Northwest. (a) 2000 emissions (b) 2050 emissions Change of summer 90 th percentile max-8h O 3 due to climate change

14. Translating climate change penalty to emission control efforts 2000 conditions NOx emission - 40% (2000 climate) NOx emission - 40% (2050 climate) NOx emissions - 50% (2050 climate) 2000–2050 climate change implies an additional 25% effort in NOx emission controls to achieve the same ozone air quality.

15. Conclusions 1.Climate change is expected to worsen the U.S. ozone air quality; the summer average daily max-8h ozone is projected to increase by 2-5 ppb over large areas due to 2000-2050 climate change with the IPCC A1B scenario. Climate change has most effects on air pollution episodes than on the means; it increases the 90th percentile ozone by up to 10 ppb. 2.The 2000-2050 changes in anthropogenic emissions of ozone precursors outside of North America would increase the mean summer PRB ozone by 3-6 ppb in the western United States, and by 2-3 ppb in the East. 3.Factors causing worse ozone air quality associated with the future climate include: higher temperature, less convection, lower mixing depth, higher natural emissions as well as less frequent cyclones. 4.Preliminary analysis suggests that the climate change penalty corresponds to a need for some 10% further reductions in NO x emissions to meet our goals for clean air. 5.Emission reductions can greatly mitigate the “climate change penalty” for ozone air quality, and can even turn it into a “climate benefit”.